22 – Aboveground Tanks

location (siting) of aboveground tanks  separation distance from  nearest important building  near and far side of public way  property line that is or can be built upon  shell-to-shell spacing
10
. at grade. concrete or steel
Ch. 22 – Aboveground Tanks

tank supports and foundation  design to minimize excessive loading at supports and to minimize uneven settling  design for earthquakes  on ground or on supports of masonry. below grade without backfill
Ch.Ch. 22 – Aboveground Tanks

covers tanks installed above grade.

22 .  dike capacity = the greatest volume of qu d that can e eased o t e a gest liquid t at ca be released from the largest tank (overflow point)  local law might require more  capacity calculated by deducting from gross volume of diked area the volume of all enclosed tanks below height of dike wall. 23 .Impounding by Diking
Ch. except for the largest tank
Ch.Aboveground Tanks

spill control – diking  1% slope from tank to dike wall for 50 ft.Underground Tanks
1.48
16
.

footings. with respect to existing foundations.Underground Tanks

general installation requirements  must be installed in accordance with manufacturer’s instructions  excavation must not undermine foundations or footings of existing structures  tanks must not be damaged during delivery. so that loads are not pp transmitted to the tank itself
Basement or Pit Class I Class II 1 ft 1 ft
Property Line 3 ft 1 ft
17
. and supports. 23 . unloading.Ch. 23 . or placement into the excavation
Ch.Underground Tanks

tank location  tank must be situated.

must have a tight fill device for connecting the fill hose to the tank
Ch.000 gal. 23 .Underground Tanks

tank openings other than vents  fill and discharge lines can enter tank only through the top  slope fill lines toward the tank  tanks for Class I liquids with a capacity > 1.14 for requirements  tanks must be anchored so that they cannot float out of the ground when subjected to maximum groundwater level j g or flood stage
20
.Underground Tanks

tank openings other than vents  connections must be liquid & vapor tight  gauge openings must have liquid & vapor tight caps or covers  covers kept closed when not in use  inside building.Underground Tanks

see Section 23. protect each opening against liquid overflow and vapor release  use a spring-loaded check valve or other approved device
Ch. 23 . 23 .Ch.

4. 1 ft = 0.1(a).4. or from Nearest Including the Opposite Side Important Building of a Public Waya on the Same Propertya ½ × diameter of tank Diameter of tank but need not exceed 175 ft ½ × diameter of tank
1 1
Type of Tank
Protection
Floating roof
Protection for exposuresb None Approved foam or inerting systemc on tanks not exceeding 150 ft in diameterd Protection for exposuresb None
/6 × diameter of tank /6 × diameter of tank /6 × diameter of tank
Vertical with weak roof-toshell seam
1
Diameter of tank 2 × diameter of tank but need not exceed 350 ft ½ × value in Table 22.000 1.3.
Table 22. Standard on Explosion Prevention Systems.1.4.1.5 Minimum Distance (ft) From Nearest Side of Any Public Way or From Property Line That Is or Can Be Built from Nearest Important Building on the Upon.4.1.4. aThe minimum distance cannot be less than 5 ft (1.1.001 to 1.Table 22.001 or more
.5 m).4.000 50.1.000 500.1(b) Value in Table 22.4.1.4.001 to 50. use “Protection for Exposures” or “None.000.1.1(b) ½ × value in Table 22.42.4.3 m. 1 ft = 0. Including the Opposite Side of a Same Property Public Way 5 5 10 5 15 5 20 5 30 10 50 15 80 25 100 35 135 45 165 55 175 60 For SI units.001 to 3.000 100.1.1(b)
Value in Table 22.4.000. 1 gal = 3. dFor tanks over 150 ft (45 m) in diameter.1.1(b) 2 × value in Table 22.000.000 30. and 22.001 to 2.000 3.000.
Tank Capacity (gal)
275 or less 276 to 750 751 to 12.5 psi (gauge pressure of 17 kPa) Protection for exposuresb None Protected aboveground tank None
½ × value in Table 22. bSee definition 3.1(b) Reference Table for Use with Tables 22.4.1.1(a) Location of Aboveground Storage Tanks Storing Stable Liquids — Internal Pressure Not to Exceed a Gauge Pressure of 2.000.1.3 m.1(b)
1 1
/3 × diameter of tank /3 × diameter of tank
Horizontal and vertical tanks Approved inerting systemb on with emergency relief the tank or approved foam venting to limit pressures to system on vertical tanks 2.1.1(b)
For SI units.3.1(b) ½ × value in Table 22.” as applicable.4.000 2.1.1(b)
Value in Table 22.001 to 500. Protection for Exposures.000.5 psi (17 kPa) Minimum Distance (ft) From Nearest Side From Property Line That Is of Any Public Way or Can Be Built Upon. 22.000 12.4.001 to 100.001 to 30. cSee NFPA 69.8 L.

Table 22.4.4.9 m) 3 ft (0.1(b) but not less than 150 ft
Not less than 100 ft Not less than 150 ft
For SI units.2 diameters
¼ × sum of adjacent tank diameters
1
/6 × sum of adjacent tank diameters
/3 × sum of adjacent tank diameters
¼ × sum of adjacent tank diameters
.4.4.2. approved barricade Protection for exposuresb None
Horizontal and vertical tanks with emergency relief venting to permit pressure over a gauge pressure of 2.4. approved inerting.3 m.42. Including the Building on the Same Opposite Side of a Public Way Propertya Not less than 25 ft Value in Table 22. Standard on Explosion Prevention Systems.1.4.1.a approved insulation and refrigeration. aSee NFPA 69.1 Minimum Shell-to-Shell Spacing of Aboveground Storage Tanks Fixed or Horizontal Tanks Class I or II Liquids Class IIIA Liquids 1/6 × sum of adjacent tank 1/6 × sum of adjacent tank diameters but not less than diameters but not less than 3 ft (0.1(b) but not less than 100 ft 8 × value in Table 22.11.4.5 Location of Aboveground Storage Tanks Storing Unstable Liquids Minimum Distance (ft) From Nearest Side of From Property Line Any Public Way or from that Is or Can Be Built Nearest Important Upon.1 If open diking is provided in ¼ × sum of adjacent tank accordance with 22.1(b) but not less than 100 ft 2 × value in Table 22. bSee definition 3.a approved insulation and refrigeration.
Table 22.1.5 psi (17 kPa)
Tank protected with any one of the following: approved water spray. approved barricade Protection for exposuresb None
2½ × value in Table 22. approved inerting.1(b) but not less than 50 ft 5 × value in Table 22. Protection for Exposures.1.1(b) but not less than 25 ft
Type of Tank
Protection
Horizontal and vertical tanks with emergency relief venting to permit pressure not in excess of a gauge pressure of 2.1.1. 1 ft = 0.1.5 psi (17 kPa)
Tank protected with any one of the following: approved water spray.9 m)
1
Tank Diameter Floating Roof Tanks All tanks not over 150 ft (45 m) 1/6 × sum of adjacent tank in diameter diameters but not less than 3 ft (0.11.9 m) Tanks larger than 150 ft (45 m) in diameter: 1 If remote impounding is /6 × sum of adjacent tank provided in accordance with diameters 22.3.4.1(b) but not less than 50 ft
Not less than 50 ft
Not less than 100 ft
Not less than 50 ft
4 × value in Table 22.

A. The tank storing No. Flammable and Combustible Liquids Code. 1. B.5 psig. Each tank has a capacity of 20. The steel tank supports are 12 in. The gasoline tanks to the near side and opposite side of the street. 2. high at the lowest point of the saddles and can be ignored in the calculation of dike capacity. The tank storing No. The area of the interior of the dike is 60 ft. 3. The tank storing No. 1 fuel oil to the loading rack. 5. measured at the interior toe. 1 Separation Distances & Diking Requirements
Verify that the small bulk plant shown on the next page complies with the minimum separation distance provisions of NFPA 30. 4. 2 fuel oil to the property line adjacent to the warehouse.
. and the height of the dike wall. Determine the minimum distances required from: The gasoline tank to the property line adjoining the vacant lot.Case Study No.700 L). 1 fuel oil to the office building. The right hand property line coincides with the near side of the public road. Protection for exposed properties ia assumed.000 gal (25. is 12 in. by 40 ft. Determine if the facility meets the spill control requirements of NFPA 30. All four tanks are horizontal and equipped with emergency relief venting to limit pressures to 2.

Case Study No. 1 Separation Distances & Diking Requirements
.

the shell-to-shell spacing. Tank #3 to the property line and to the process building. 2 Separation Distances & Diking Requirements
Evaluate site plans for the process plant depicted on the next page and verify compliance with the minimum separation distance provisions of NFPA 30. in diameter and 30 ft. A. that is. The tanks to the near side of the street. Flammable and Combustible Liquids Code. The area of the interior of the dike is 50 ft. One tank to another. Tank #3 is a vertical fixed roof tank with emergency relief venting to permit internal pressure to rise no greater than 2. The right hand property line coincides with the near side of the street. high. Tanks #1 and #2 are vertical fixed roof tanks with weak roof-to-shell seams and are 25 ft. The tanks to the far side of the street. 3. The process building houses process vessels. Tank #2 contains 100. by 80 ft. Determine if the facility meets the spill control requirements of NFPA 30.5 psig. The wall of the process building facing the adjacent property is a blank. and the height of the dike wall.000 gal of xylene. is 18 in.000 gal of toluene. high. measured at the interior toe. B. 2-hour rated fire wall.
. high. which is considered an unstable liquid. This tank is 20 ft. It contains 70.Case Study No. 4. a stable Class I liquid. Tank #1 contains 100. in diameter and 30 ft. Determine the required distance from: The process building to the property line. The tank is insulated and protected with a water spray system. 5.000 gal of styrene. 1. 6. also a stable Class I liquid. 2. Tank #1 to the process building.